This is a competing renewal application that requests continued support for providing pre- and postdoctoral trainees with strong methodological and practical training in quantitative cancer research at the Harvard Public School of Public Health and Dana-Farber Cancer Institute (DFCI). This training program, now in its 30th year, draws upon a distinguished faculty, consisting of biostatisticians and computational biologists, as well as world renowned experts in cancer treatment and research. Its overarching goal is to provide the trainees with all essential elements of training needed to successfully undertake modern cancer research. The specific goals of this training program are to train students and postdoctoral fellows to be (1) quantitative scientists in cancer research, who are capable of using probability, statistics, computer science and mathematics to increase our knowledge and understanding of cancer; (2) strong team leaders/players as well as excellent communicators in a cancer research environment, who can effectively disseminate their research results and assume active roles in the design, analysis and interpretation of cancer clinical trials, cancer prevention trials and cancer genomic studies. All predoctoral students supported by this training grant are required to take a concentration in cancer-related courses. During their first and second summer periods in the program, students are required to participate in research activities of the Dana-Farber Cancer Institute (DFCI), performed under the supervision of faculty mentor/trainers affiliated in the program. Afterwards, many of these students will take up residence at the DFCI and continue their research in cancer, which eventually evolves into their dissertation projects. All the postdoctoral fellows are closely involved with the practice of quantitative sciences in cancer and are in residence at the DFCI. All trainees are required to actively participate in the a working group seminar series on quantitative issues in cancer research, which serves as a primary forum at Harvard to discuss current issues and challenges on this topic. This proposal requests funding to support 10 pre-doctoral students and 1 post-doctoral fellow for 5 years.